"What do you mean by writing the name of the place in invisible ink?" "Never did such a thing, sir. Don’t know anything about invisible ink." "Well, how do you explain it, then? This card had the name written in invisible ink. It was discovered by the Post Office in London, and they’ve returned it for inquiries. What have you to say?" "What I said before, sir: I didn’t do it." "You write to Henry Smith, 563 Pentonville Road?" "Never heard of him, sir." "What’s the game, then? Go and fetch the post corporal," he said to his servant. The man came in with a bundle of recently collected cards in his hand. "Look at this," said the captain, showing him the card in question. "Did you get that from Murgatroyd?" "I couldn’t say, sir; I get such a lot." "But you know his signature?" "I can’t say I do, sir; but he has just written a card; perhaps you would like to have a look at it." He searched his bundle, found the card and handed it to the captain, who compared the two signatures. "This is very odd," he said. "They are very much alike, but there’s a slight difference in the shape of the y. It looks as though some one were imitating your fist, Murgatroyd." "Yes, sir," said Ginger, stiffly. "I’d like to punch his head, sir," he added, as the baseness of the trick struck him. "Well, we must find out who it is. Keep this to yourselves, men; he may try it again and give us a chance to catch him. Not a word to anyone, mind." Ginger saluted and returned to his billet, his indignation growing at every step. The incident was discussed at the officers’ mess that night. "Murgatroyd is straight enough," said Kennedy. "He’s one of the best men in my platoon. It’s rather a mean trick." "And a senseless one," said the captain. "I’m inclined to think one of the men must owe him a grudge, and want to get him into trouble." "What about the addressee?" asked another officer. "Who is Henry Smith, of 563 Pentonville Road?" "The London people will keep him under observation, no doubt," said the captain. "I told the post corporal to examine every batch carefully, and see if there are any more addressed to the same person." Three days passed. No letters or cards addressed to Henry Smith were discovered. On the third day a telegram from London was delivered to the colonel. "Henry Smith gone, leaving no address. Report result of enquiry." After consulting Captain Adams the colonel telegraphed in reply that Murgatroyd’s signature appeared to have been forged, probably with the intention of getting him into trouble, and that he was keeping a careful watch on the correspondence. Ginger meanwhile had recovered his spirits. He had been made a lance-corporal, and sewed the stripe on his sleeve with ingenuous satisfaction. At the back of his mind was a suspicion that Stoneway might have sought a mean revenge for his thrashing by this use of invisible ink; but since the scheme had failed, he resolved not to trouble his head about it.